Processes for recycling used or in-process defective batteries (hereinafter referred to as “waste batteries”), such as waste lithium-ion batteries, and recovering their valuable metals are broadly divided into dry and wet processes.
A dry process includes melting crushed waste batteries, separating valuable metals such as cobalt, nickel, and copper, which are to be recovered, from other less valuable metals and materials such as iron and aluminium by harnessing the difference in oxygen affinity between them, and recovering the valuable metals. Specifically, such a dry process includes oxidizing less valuable elements, such as iron, as much as possible to form slag and suppressing the oxidation of valuable materials, such as cobalt, as much as possible to recover the valuable materials in the form of an alloy.
For example, Patent Document 1 discloses a method using a high-temperature heating furnace, in which a flux is added to waste batteries, and slag is repeatedly treated so that valuable metals such as nickel and cobalt can be recovered at a rate of around 80%.    [Patent Document 1] U.S. Pat. No. 7,169,206